Hepatocytes, isolated from the livers of fasted male rats, will be incubated with a mixture of substrates, one of which will be labeled with 14C. Measurements will be made of the amount of label released from each labeled substrate as 14CO2, and the amounts incorporated into glycogen, into glucose released into the medium, into the fatty acyl and glycerol moieties of lipids, and into some other products as well. These measurements, which will be performed in the presence and absence of the hormone vasopressin (known to affect glycogen metabolism in hepatocytes) will provide the necessary data for an analysis of carbon flux along the glycolytic, glycogenic, and pentose-phosphate pathways in liver cells. Similar experiments have been performed on the ciliated protozoan Tetrahymena pyriformis, and have led to the finding that calmodulin, a Ca2 ion-sensitive protein involved in the control of glycogen metabolism in the metazoa, is present in this protozoan. Preliminary studies indicate that the glycogen metabolism of Tetrahymena is inhibited by chlorpromazine, a drug known to react with and inhibit the functions of calmodulin. Studies will also be performed on the control of glycogen metabolism in Tetrahymena as part of the continuing work on the organization of metabolism in this cell.